Two of three anomalous crater chains on Ganymede are shown here. The chain on the left is 60 km long, and is believed to have formed when a comet split by Jupiter into6 fragments hit Ganymede. The chain on the right is 160 km long and also formed when a split comet hit Ganymede. The sizes of these craters and the morphologies of these crater chains are being studied to determine the properties of cometary nuclei, and the nature of the comet splitting process.
